src/interpreter/mod.rs

   1 use rustc::middle::const_val;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::mir_map::MirMap;
   4 use rustc::mir::repr as mir;
   5 use rustc::traits::{self, ProjectionMode};
   6 use rustc::ty::fold::TypeFoldable;
   7 use rustc::ty::layout::{self, Layout, Size};
   8 use rustc::ty::subst::{self, Subst, Substs};
   9 use rustc::ty::{self, Ty, TyCtxt};
  10 use rustc::util::nodemap::DefIdMap;
  11 use std::cell::RefCell;
  12 use std::ops::Deref;
  13 use std::rc::Rc;
  14 use std::{iter, mem};
  15 use syntax::ast;
  16 use syntax::attr;
  17 use syntax::codemap::{self, DUMMY_SP};
  18
  19 use error::{EvalError, EvalResult};
  20 use memory::{Memory, Pointer};
  21 use primval::{self, PrimVal};
  22
  23 use std::collections::HashMap;
  24
  25 mod stepper;
  26
  27 struct GlobalEvalContext<'a, 'tcx: 'a> {
  28     /// The results of the type checker, from rustc.
  29     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  30
  31     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  32     mir_map: &'a MirMap<'tcx>,
  33
  34     /// A local cache from DefIds to Mir for non-crate-local items.
  35     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  36
  37     /// The virtual memory system.
  38     memory: Memory,
  39
  40     /// Precomputed statics, constants and promoteds
  41     statics: HashMap<ConstantId<'tcx>, Pointer>,
  42
  43     /// The virtual call stack.
  44     stack: Vec<Frame<'a, 'tcx>>,
  45 }
  46
  47 /// A stack frame.
  48 struct Frame<'a, 'tcx: 'a> {
  49     /// The def_id of the current function
  50     def_id: DefId,
  51
  52     /// The span of the call site
  53     span: codemap::Span,
  54
  55     /// type substitutions for the current function invocation
  56     substs: &'tcx Substs<'tcx>,
  57
  58     /// The MIR for the function called on this frame.
  59     mir: CachedMir<'a, 'tcx>,
  60
  61     /// The block that is currently executed (or will be executed after the above call stacks return)
  62     next_block: mir::BasicBlock,
  63
  64     /// A pointer for writing the return value of the current call if it's not a diverging call.
  65     return_ptr: Option<Pointer>,
  66
  67     /// The list of locals for the current function, stored in order as
  68     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  69     /// and the temporaries at `self.temp_offset`.
  70     locals: Vec<Pointer>,
  71
  72     /// The offset of the first variable in `self.locals`.
  73     var_offset: usize,
  74
  75     /// The offset of the first temporary in `self.locals`.
  76     temp_offset: usize,
  77
  78     /// The index of the currently evaluated statment
  79     stmt: usize,
  80 }
  81
  82 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  83 struct Lvalue {
  84     ptr: Pointer,
  85     extra: LvalueExtra,
  86 }
  87
  88 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  89 enum LvalueExtra {
  90     None,
  91     Length(u64),
  92     // TODO(solson): Vtable(memory::AllocId),
  93     DowncastVariant(usize),
  94 }
  95
  96 #[derive(Clone)]
  97 enum CachedMir<'mir, 'tcx: 'mir> {
  98     Ref(&'mir mir::Mir<'tcx>),
  99     Owned(Rc<mir::Mir<'tcx>>)
 100 }
 101
 102 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 103 enum TerminatorTarget {
 104     /// Make a local jump to the next block
 105     Block,
 106
 107     /// Start executing from the new current frame. (For function calls.)
 108     Call,
 109
 110     /// Stop executing the current frame and resume the previous frame.
 111     Return,
 112 }
 113
 114 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 115 /// Uniquely identifies a specific constant or static
 116 struct ConstantId<'tcx> {
 117     /// the def id of the constant/static or in case of promoteds, the def id of the function they belong to
 118     def_id: DefId,
 119     /// In case of statics and constants this is `Substs::empty()`, so only promoteds and associated
 120     /// constants actually have something useful here. We could special case statics and constants,
 121     /// but that would only require more branching when working with constants, and not bring any
 122     /// real benefits.
 123     substs: &'tcx Substs<'tcx>,
 124     kind: ConstantKind,
 125 }
 126
 127 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 128 enum ConstantKind {
 129     Promoted(usize),
 130     /// Statics, constants and associated constants
 131     Global,
 132 }
 133
 134 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 135     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 136         GlobalEvalContext {
 137             tcx: tcx,
 138             mir_map: mir_map,
 139             mir_cache: RefCell::new(DefIdMap()),
 140             memory: Memory::new(tcx.sess
 141                                    .target
 142                                    .uint_type
 143                                    .bit_width()
 144                                    .expect("Session::target::uint_type was usize")/8),
 145             statics: HashMap::new(),
 146             stack: Vec::new(),
 147         }
 148     }
 149
 150     fn call(&mut self, mir: &'a mir::Mir<'tcx>, def_id: DefId) -> EvalResult<Option<Pointer>> {
 151         let substs = self.tcx.mk_substs(subst::Substs::empty());
 152         let return_ptr = self.alloc_ret_ptr(mir.return_ty, substs);
 153
 154         self.push_stack_frame(def_id, mir.span, CachedMir::Ref(mir), substs, None);
 155
 156         self.frame_mut().return_ptr = return_ptr;
 157
 158         self.run()?;
 159         Ok(return_ptr)
 160     }
 161
 162     fn alloc_ret_ptr(&mut self, output_ty: ty::FnOutput<'tcx>, substs: &'tcx Substs<'tcx>) -> Option<Pointer> {
 163         match output_ty {
 164             ty::FnConverging(ty) => {
 165                 let size = self.type_size(ty, substs);
 166                 Some(self.memory.allocate(size))
 167             }
 168             ty::FnDiverging => None,
 169         }
 170     }
 171
 172     // TODO(solson): Try making const_to_primval instead.
 173     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
 174         use rustc::middle::const_val::ConstVal::*;
 175         match *const_val {
 176             Float(_f) => unimplemented!(),
 177             Integral(int) => {
 178                 // TODO(solson): Check int constant type.
 179                 let ptr = self.memory.allocate(8);
 180                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
 181                 Ok(ptr)
 182             }
 183             Str(ref s) => {
 184                 let psize = self.memory.pointer_size;
 185                 let static_ptr = self.memory.allocate(s.len());
 186                 let ptr = self.memory.allocate(psize * 2);
 187                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
 188                 self.memory.write_ptr(ptr, static_ptr)?;
 189                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
 190                 Ok(ptr)
 191             }
 192             ByteStr(ref bs) => {
 193                 let psize = self.memory.pointer_size;
 194                 let static_ptr = self.memory.allocate(bs.len());
 195                 let ptr = self.memory.allocate(psize);
 196                 self.memory.write_bytes(static_ptr, bs)?;
 197                 self.memory.write_ptr(ptr, static_ptr)?;
 198                 Ok(ptr)
 199             }
 200             Bool(b) => {
 201                 let ptr = self.memory.allocate(1);
 202                 self.memory.write_bool(ptr, b)?;
 203                 Ok(ptr)
 204             }
 205             Char(_c)          => unimplemented!(),
 206             Struct(_node_id)  => unimplemented!(),
 207             Tuple(_node_id)   => unimplemented!(),
 208             Function(_def_id) => unimplemented!(),
 209             Array(_, _)       => unimplemented!(),
 210             Repeat(_, _)      => unimplemented!(),
 211             Dummy             => unimplemented!(),
 212         }
 213     }
 214
 215     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
 216         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
 217     }
 218
 219     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
 220         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
 221     }
 222
 223     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
 224         // Do the initial selection for the obligation. This yields the shallow result we are
 225         // looking for -- that is, what specific impl.
 226         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 227             let mut selcx = traits::SelectionContext::new(&infcx);
 228
 229             let obligation = traits::Obligation::new(
 230                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
 231                 trait_ref.to_poly_trait_predicate(),
 232             );
 233             let selection = selcx.select(&obligation).unwrap().unwrap();
 234
 235             // Currently, we use a fulfillment context to completely resolve all nested obligations.
 236             // This is because they can inform the inference of the impl's type parameters.
 237             let mut fulfill_cx = traits::FulfillmentContext::new();
 238             let vtable = selection.map(|predicate| {
 239                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
 240             });
 241             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
 242         })
 243     }
 244
 245     /// Trait method, which has to be resolved to an impl method.
 246     pub fn trait_method(
 247         &self,
 248         def_id: DefId,
 249         substs: &'tcx Substs<'tcx>
 250     ) -> (DefId, &'tcx Substs<'tcx>) {
 251         let method_item = self.tcx.impl_or_trait_item(def_id);
 252         let trait_id = method_item.container().id();
 253         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
 254         match self.fulfill_obligation(trait_ref) {
 255             traits::VtableImpl(vtable_impl) => {
 256                 let impl_did = vtable_impl.impl_def_id;
 257                 let mname = self.tcx.item_name(def_id);
 258                 // Create a concatenated set of substitutions which includes those from the impl
 259                 // and those from the method:
 260                 let impl_substs = vtable_impl.substs.with_method_from(substs);
 261                 let substs = self.tcx.mk_substs(impl_substs);
 262                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
 263
 264                 (mth.method.def_id, mth.substs)
 265             }
 266
 267             traits::VtableClosure(vtable_closure) =>
 268                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
 269
 270             traits::VtableFnPointer(_fn_ty) => {
 271                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
 272                 unimplemented!()
 273                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
 274
 275                 // let method_ty = def_ty(tcx, def_id, substs);
 276                 // let fn_ptr_ty = match method_ty.sty {
 277                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
 278                 //     _ => unreachable!("expected fn item type, found {}",
 279                 //                       method_ty)
 280                 // };
 281                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
 282             }
 283
 284             traits::VtableObject(ref _data) => {
 285                 unimplemented!()
 286                 // Callee {
 287                 //     data: Virtual(traits::get_vtable_index_of_object_method(
 288                 //                   tcx, data, def_id)),
 289                 //                   ty: def_ty(tcx, def_id, substs)
 290                 // }
 291             }
 292             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
 293         }
 294     }
 295
 296     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
 297         match self.tcx.map.as_local_node_id(def_id) {
 298             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
 299             None => {
 300                 let mut mir_cache = self.mir_cache.borrow_mut();
 301                 if let Some(mir) = mir_cache.get(&def_id) {
 302                     return CachedMir::Owned(mir.clone());
 303                 }
 304
 305                 let cs = &self.tcx.sess.cstore;
 306                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
 307                     panic!("no mir for {:?}", def_id);
 308                 });
 309                 let cached = Rc::new(mir);
 310                 mir_cache.insert(def_id, cached.clone());
 311                 CachedMir::Owned(cached)
 312             }
 313         }
 314     }
 315
 316     fn monomorphize(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
 317         let substituted = ty.subst(self.tcx, substs);
 318         self.tcx.normalize_associated_type(&substituted)
 319     }
 320
 321     fn type_size(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> usize {
 322         self.type_layout(ty, substs).size(&self.tcx.data_layout).bytes() as usize
 323     }
 324
 325     fn type_layout(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> &'tcx Layout {
 326         // TODO(solson): Is this inefficient? Needs investigation.
 327         let ty = self.monomorphize(ty, substs);
 328
 329         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 330             // TODO(solson): Report this error properly.
 331             ty.layout(&infcx).unwrap()
 332         })
 333     }
 334
 335     #[inline(never)]
 336     #[cold]
 337     fn report(&self, e: &EvalError) {
 338         let stmt = self.frame().stmt;
 339         let block = self.basic_block();
 340         let span = if stmt < block.statements.len() {
 341             block.statements[stmt].span
 342         } else {
 343             block.terminator().span
 344         };
 345         let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 346         for &Frame{ def_id, substs, span, .. } in self.stack.iter().rev() {
 347             // FIXME(solson): Find a way to do this without this Display impl hack.
 348             use rustc::util::ppaux;
 349             use std::fmt;
 350             struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 351             impl<'tcx> fmt::Display for Instance<'tcx> {
 352                 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 353                     ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 354                         |tcx| tcx.lookup_item_type(self.0).generics)
 355                 }
 356             }
 357             err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 358         }
 359         err.emit();
 360     }
 361
 362     fn maybe_report<T>(&self, r: EvalResult<T>) -> EvalResult<T> {
 363         if let Err(ref e) = r {
 364             self.report(e);
 365         }
 366         r
 367     }
 368
 369     fn run(&mut self) -> EvalResult<()> {
 370         let mut stepper = stepper::Stepper::new(self);
 371         while stepper.step()? {}
 372         Ok(())
 373     }
 374
 375     fn push_stack_frame(&mut self, def_id: DefId, span: codemap::Span, mir: CachedMir<'a, 'tcx>, substs: &'tcx Substs<'tcx>,
 376         return_ptr: Option<Pointer>)
 377     {
 378         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 379         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 380         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 381
 382         let num_args = mir.arg_decls.len();
 383         let num_vars = mir.var_decls.len();
 384
 385         ::log_settings::settings().indentation += 1;
 386
 387         self.stack.push(Frame {
 388             mir: mir.clone(),
 389             next_block: mir::START_BLOCK,
 390             return_ptr: return_ptr,
 391             locals: Vec::new(),
 392             var_offset: num_args,
 393             temp_offset: num_args + num_vars,
 394             span: span,
 395             def_id: def_id,
 396             substs: substs,
 397             stmt: 0,
 398         });
 399
 400         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 401             let size = self.type_size(ty, self.substs());
 402             self.memory.allocate(size)
 403         }).collect();
 404
 405         self.frame_mut().locals = locals;
 406     }
 407
 408     fn pop_stack_frame(&mut self) {
 409         ::log_settings::settings().indentation -= 1;
 410         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 411         // TODO(solson): Deallocate local variables.
 412     }
 413
 414     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 415             -> EvalResult<TerminatorTarget> {
 416         use rustc::mir::repr::TerminatorKind::*;
 417         let target = match terminator.kind {
 418             Return => TerminatorTarget::Return,
 419
 420             Goto { target } => {
 421                 self.frame_mut().next_block = target;
 422                 TerminatorTarget::Block
 423             },
 424
 425             If { ref cond, targets: (then_target, else_target) } => {
 426                 let cond_ptr = self.eval_operand(cond)?;
 427                 let cond_val = self.memory.read_bool(cond_ptr)?;
 428                 self.frame_mut().next_block = if cond_val { then_target } else { else_target };
 429                 TerminatorTarget::Block
 430             }
 431
 432             SwitchInt { ref discr, ref values, ref targets, .. } => {
 433                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 434                 let discr_size = self
 435                     .type_layout(self.lvalue_ty(discr), self.substs())
 436                     .size(&self.tcx.data_layout)
 437                     .bytes() as usize;
 438                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 439
 440                 // Branch to the `otherwise` case by default, if no match is found.
 441                 let mut target_block = targets[targets.len() - 1];
 442
 443                 for (index, val_const) in values.iter().enumerate() {
 444                     let ptr = self.const_to_ptr(val_const)?;
 445                     let val = self.memory.read_uint(ptr, discr_size)?;
 446                     if discr_val == val {
 447                         target_block = targets[index];
 448                         break;
 449                     }
 450                 }
 451
 452                 self.frame_mut().next_block = target_block;
 453                 TerminatorTarget::Block
 454             }
 455
 456             Switch { ref discr, ref targets, adt_def } => {
 457                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 458                 let adt_ty = self.lvalue_ty(discr);
 459                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 460                 let matching = adt_def.variants.iter()
 461                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 462
 463                 match matching {
 464                     Some(i) => {
 465                         self.frame_mut().next_block = targets[i];
 466                         TerminatorTarget::Block
 467                     },
 468                     None => return Err(EvalError::InvalidDiscriminant),
 469                 }
 470             }
 471
 472             Call { ref func, ref args, ref destination, .. } => {
 473                 let mut return_ptr = None;
 474                 if let Some((ref lv, target)) = *destination {
 475                     self.frame_mut().next_block = target;
 476                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 477                 }
 478
 479                 let func_ty = self.operand_ty(func);
 480                 match func_ty.sty {
 481                     ty::TyFnDef(def_id, substs, fn_ty) => {
 482                         use syntax::abi::Abi;
 483                         match fn_ty.abi {
 484                             Abi::RustIntrinsic => {
 485                                 let name = self.tcx.item_name(def_id).as_str();
 486                                 match fn_ty.sig.0.output {
 487                                     ty::FnConverging(ty) => {
 488                                         let size = self.type_size(ty, self.substs());
 489                                         let ret = return_ptr.unwrap();
 490                                         self.call_intrinsic(&name, substs, args, ret, size)?
 491                                     }
 492                                     ty::FnDiverging => unimplemented!(),
 493                                 }
 494                             }
 495
 496                             Abi::C => {
 497                                 match fn_ty.sig.0.output {
 498                                     ty::FnConverging(ty) => {
 499                                         let size = self.type_size(ty, self.substs());
 500                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 501                                     }
 502                                     ty::FnDiverging => unimplemented!(),
 503                                 }
 504                             }
 505
 506                             Abi::Rust | Abi::RustCall => {
 507                                 // TODO(solson): Adjust the first argument when calling a Fn or
 508                                 // FnMut closure via FnOnce::call_once.
 509
 510                                 // Only trait methods can have a Self parameter.
 511                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 512                                     self.trait_method(def_id, substs)
 513                                 } else {
 514                                     (def_id, substs)
 515                                 };
 516
 517                                 let mut arg_srcs = Vec::new();
 518                                 for arg in args {
 519                                     let src = self.eval_operand(arg)?;
 520                                     let src_ty = self.operand_ty(arg);
 521                                     arg_srcs.push((src, src_ty));
 522                                 }
 523
 524                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 525                                     arg_srcs.pop();
 526                                     let last_arg = args.last().unwrap();
 527                                     let last = self.eval_operand(last_arg)?;
 528                                     let last_ty = self.operand_ty(last_arg);
 529                                     let last_layout = self.type_layout(last_ty, self.substs());
 530                                     match (&last_ty.sty, last_layout) {
 531                                         (&ty::TyTuple(fields),
 532                                          &Layout::Univariant { ref variant, .. }) => {
 533                                             let offsets = iter::once(0)
 534                                                 .chain(variant.offset_after_field.iter()
 535                                                     .map(|s| s.bytes()));
 536                                             for (offset, ty) in offsets.zip(fields) {
 537                                                 let src = last.offset(offset as isize);
 538                                                 arg_srcs.push((src, ty));
 539                                             }
 540                                         }
 541                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 542                                     }
 543                                 }
 544
 545                                 let mir = self.load_mir(resolved_def_id);
 546                                 self.push_stack_frame(def_id, terminator.span, mir, resolved_substs, return_ptr);
 547
 548                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 549                                     let dest = self.frame().locals[i];
 550                                     self.move_(src, dest, src_ty)?;
 551                                 }
 552
 553                                 TerminatorTarget::Call
 554                             }
 555
 556                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 557                         }
 558                     }
 559
 560                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 561                 }
 562             }
 563
 564             Drop { ref value, target, .. } => {
 565                 let ptr = self.eval_lvalue(value)?.to_ptr();
 566                 let ty = self.lvalue_ty(value);
 567                 self.drop(ptr, ty)?;
 568                 self.frame_mut().next_block = target;
 569                 TerminatorTarget::Block
 570             }
 571
 572             Resume => unimplemented!(),
 573         };
 574
 575         Ok(target)
 576     }
 577
 578     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 579         if !self.type_needs_drop(ty) {
 580             debug!("no need to drop {:?}", ty);
 581             return Ok(());
 582         }
 583         trace!("-need to drop {:?}", ty);
 584
 585         // TODO(solson): Call user-defined Drop::drop impls.
 586
 587         match ty.sty {
 588             ty::TyBox(contents_ty) => {
 589                 match self.memory.read_ptr(ptr) {
 590                     Ok(contents_ptr) => {
 591                         self.drop(contents_ptr, contents_ty)?;
 592                         trace!("-deallocating box");
 593                         self.memory.deallocate(contents_ptr)?;
 594                     }
 595                     Err(EvalError::ReadBytesAsPointer) => {
 596                         let size = self.memory.pointer_size;
 597                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 598                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 599                             return Ok(());
 600                         } else {
 601                             return Err(EvalError::ReadBytesAsPointer);
 602                         }
 603                     }
 604                     Err(e) => return Err(e),
 605                 }
 606             }
 607
 608             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 609             _ => {}
 610         }
 611
 612         // Filling drop.
 613         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 614         let size = self.type_size(ty, self.substs());
 615         self.memory.drop_fill(ptr, size)?;
 616
 617         Ok(())
 618     }
 619
 620     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 621         use rustc::ty::layout::Layout::*;
 622         let adt_layout = self.type_layout(adt_ty, self.substs());
 623
 624         let discr_val = match *adt_layout {
 625             General { discr, .. } | CEnum { discr, .. } => {
 626                 let discr_size = discr.size().bytes();
 627                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 628             }
 629
 630             RawNullablePointer { nndiscr, .. } => {
 631                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 632             }
 633
 634             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 635                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 636                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 637                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 638             }
 639
 640             // The discriminant_value intrinsic returns 0 for non-sum types.
 641             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 642             Vector { .. } => 0,
 643         };
 644
 645         Ok(discr_val)
 646     }
 647
 648     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 649         let not_null = match self.memory.read_usize(ptr) {
 650             Ok(0) => false,
 651             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 652             Err(e) => return Err(e),
 653         };
 654         assert!(nndiscr == 0 || nndiscr == 1);
 655         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 656     }
 657
 658     fn call_intrinsic(
 659         &mut self,
 660         name: &str,
 661         substs: &'tcx Substs<'tcx>,
 662         args: &[mir::Operand<'tcx>],
 663         dest: Pointer,
 664         dest_size: usize
 665     ) -> EvalResult<TerminatorTarget> {
 666         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 667             .map(|arg| self.eval_operand(arg))
 668             .collect();
 669         let args = args_res?;
 670
 671         match name {
 672             // FIXME(solson): Handle different integer types correctly.
 673             "add_with_overflow" => {
 674                 let ty = *substs.types.get(subst::FnSpace, 0);
 675                 let size = self.type_size(ty, self.substs());
 676                 let left = self.memory.read_int(args[0], size)?;
 677                 let right = self.memory.read_int(args[1], size)?;
 678                 let (n, overflowed) = unsafe {
 679                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 680                 };
 681                 self.memory.write_int(dest, n, size)?;
 682                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 683             }
 684
 685             "assume" => {}
 686
 687             "copy_nonoverlapping" => {
 688                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 689                 let elem_size = self.type_size(elem_ty, self.substs());
 690                 let src = self.memory.read_ptr(args[0])?;
 691                 let dest = self.memory.read_ptr(args[1])?;
 692                 let count = self.memory.read_isize(args[2])?;
 693                 self.memory.copy(src, dest, count as usize * elem_size)?;
 694             }
 695
 696             "discriminant_value" => {
 697                 let ty = *substs.types.get(subst::FnSpace, 0);
 698                 let adt_ptr = self.memory.read_ptr(args[0])?;
 699                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 700                 self.memory.write_uint(dest, discr_val, dest_size)?;
 701             }
 702
 703             "forget" => {
 704                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 705                 let arg_size = self.type_size(arg_ty, self.substs());
 706                 self.memory.drop_fill(args[0], arg_size)?;
 707             }
 708
 709             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 710
 711             "min_align_of" => {
 712                 self.memory.write_int(dest, 1, dest_size)?;
 713             }
 714
 715             "move_val_init" => {
 716                 let ty = *substs.types.get(subst::FnSpace, 0);
 717                 let ptr = self.memory.read_ptr(args[0])?;
 718                 self.move_(args[1], ptr, ty)?;
 719             }
 720
 721             // FIXME(solson): Handle different integer types correctly.
 722             "mul_with_overflow" => {
 723                 let ty = *substs.types.get(subst::FnSpace, 0);
 724                 let size = self.type_size(ty, self.substs());
 725                 let left = self.memory.read_int(args[0], size)?;
 726                 let right = self.memory.read_int(args[1], size)?;
 727                 let (n, overflowed) = unsafe {
 728                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 729                 };
 730                 self.memory.write_int(dest, n, size)?;
 731                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 732             }
 733
 734             "offset" => {
 735                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 736                 let pointee_size = self.type_size(pointee_ty, self.substs()) as isize;
 737                 let ptr_arg = args[0];
 738                 let offset = self.memory.read_isize(args[1])?;
 739
 740                 match self.memory.read_ptr(ptr_arg) {
 741                     Ok(ptr) => {
 742                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 743                         self.memory.write_ptr(dest, result_ptr)?;
 744                     }
 745                     Err(EvalError::ReadBytesAsPointer) => {
 746                         let addr = self.memory.read_isize(ptr_arg)?;
 747                         let result_addr = addr + offset * pointee_size as i64;
 748                         self.memory.write_isize(dest, result_addr)?;
 749                     }
 750                     Err(e) => return Err(e),
 751                 }
 752             }
 753
 754             // FIXME(solson): Handle different integer types correctly. Use primvals?
 755             "overflowing_sub" => {
 756                 let ty = *substs.types.get(subst::FnSpace, 0);
 757                 let size = self.type_size(ty, self.substs());
 758                 let left = self.memory.read_int(args[0], size)?;
 759                 let right = self.memory.read_int(args[1], size)?;
 760                 let n = left.wrapping_sub(right);
 761                 self.memory.write_int(dest, n, size)?;
 762             }
 763
 764             "size_of" => {
 765                 let ty = *substs.types.get(subst::FnSpace, 0);
 766                 let size = self.type_size(ty, self.substs()) as u64;
 767                 self.memory.write_uint(dest, size, dest_size)?;
 768             }
 769
 770             "size_of_val" => {
 771                 let ty = *substs.types.get(subst::FnSpace, 0);
 772                 if self.type_is_sized(ty) {
 773                     let size = self.type_size(ty, self.substs()) as u64;
 774                     self.memory.write_uint(dest, size, dest_size)?;
 775                 } else {
 776                     match ty.sty {
 777                         ty::TySlice(_) | ty::TyStr => {
 778                             let elem_ty = ty.sequence_element_type(self.tcx);
 779                             let elem_size = self.type_size(elem_ty, self.substs()) as u64;
 780                             let ptr_size = self.memory.pointer_size as isize;
 781                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 782                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 783                         }
 784
 785                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 786                     }
 787                 }
 788             }
 789
 790             "transmute" => {
 791                 let ty = *substs.types.get(subst::FnSpace, 0);
 792                 self.move_(args[0], dest, ty)?;
 793             }
 794             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 795
 796             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 797         }
 798
 799         // Since we pushed no stack frame, the main loop will act
 800         // as if the call just completed and it's returning to the
 801         // current frame.
 802         Ok(TerminatorTarget::Call)
 803     }
 804
 805     fn call_c_abi(
 806         &mut self,
 807         def_id: DefId,
 808         args: &[mir::Operand<'tcx>],
 809         dest: Pointer,
 810         dest_size: usize,
 811     ) -> EvalResult<TerminatorTarget> {
 812         let name = self.tcx.item_name(def_id);
 813         let attrs = self.tcx.get_attrs(def_id);
 814         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 815             Some(ln) => ln.clone(),
 816             None => name.as_str(),
 817         };
 818
 819         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 820             .map(|arg| self.eval_operand(arg))
 821             .collect();
 822         let args = args_res?;
 823
 824         match &link_name[..] {
 825             "__rust_allocate" => {
 826                 let size = self.memory.read_usize(args[0])?;
 827                 let ptr = self.memory.allocate(size as usize);
 828                 self.memory.write_ptr(dest, ptr)?;
 829             }
 830
 831             "__rust_reallocate" => {
 832                 let ptr = self.memory.read_ptr(args[0])?;
 833                 let size = self.memory.read_usize(args[2])?;
 834                 self.memory.reallocate(ptr, size as usize)?;
 835                 self.memory.write_ptr(dest, ptr)?;
 836             }
 837
 838             "memcmp" => {
 839                 let left = self.memory.read_ptr(args[0])?;
 840                 let right = self.memory.read_ptr(args[1])?;
 841                 let n = self.memory.read_usize(args[2])? as usize;
 842
 843                 let result = {
 844                     let left_bytes = self.memory.read_bytes(left, n)?;
 845                     let right_bytes = self.memory.read_bytes(right, n)?;
 846
 847                     use std::cmp::Ordering::*;
 848                     match left_bytes.cmp(right_bytes) {
 849                         Less => -1,
 850                         Equal => 0,
 851                         Greater => 1,
 852                     }
 853                 };
 854
 855                 self.memory.write_int(dest, result, dest_size)?;
 856             }
 857
 858             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 859         }
 860
 861         // Since we pushed no stack frame, the main loop will act
 862         // as if the call just completed and it's returning to the
 863         // current frame.
 864         Ok(TerminatorTarget::Call)
 865     }
 866
 867     fn assign_fields<I: IntoIterator<Item = u64>>(
 868         &mut self,
 869         dest: Pointer,
 870         offsets: I,
 871         operands: &[mir::Operand<'tcx>],
 872     ) -> EvalResult<()> {
 873         for (offset, operand) in offsets.into_iter().zip(operands) {
 874             let src = self.eval_operand(operand)?;
 875             let src_ty = self.operand_ty(operand);
 876             let field_dest = dest.offset(offset as isize);
 877             self.move_(src, field_dest, src_ty)?;
 878         }
 879         Ok(())
 880     }
 881
 882     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 883         -> EvalResult<()>
 884     {
 885         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 886         let dest_ty = self.lvalue_ty(lvalue);
 887         let dest_layout = self.type_layout(dest_ty, self.substs());
 888
 889         use rustc::mir::repr::Rvalue::*;
 890         match *rvalue {
 891             Use(ref operand) => {
 892                 let src = self.eval_operand(operand)?;
 893                 self.move_(src, dest, dest_ty)?;
 894             }
 895
 896             BinaryOp(bin_op, ref left, ref right) => {
 897                 let left_ptr = self.eval_operand(left)?;
 898                 let left_ty = self.operand_ty(left);
 899                 let left_val = self.read_primval(left_ptr, left_ty)?;
 900
 901                 let right_ptr = self.eval_operand(right)?;
 902                 let right_ty = self.operand_ty(right);
 903                 let right_val = self.read_primval(right_ptr, right_ty)?;
 904
 905                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 906                 self.memory.write_primval(dest, val)?;
 907             }
 908
 909             UnaryOp(un_op, ref operand) => {
 910                 let ptr = self.eval_operand(operand)?;
 911                 let ty = self.operand_ty(operand);
 912                 let val = self.read_primval(ptr, ty)?;
 913                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 914             }
 915
 916             Aggregate(ref kind, ref operands) => {
 917                 use rustc::ty::layout::Layout::*;
 918                 match *dest_layout {
 919                     Univariant { ref variant, .. } => {
 920                         let offsets = iter::once(0)
 921                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 922                         self.assign_fields(dest, offsets, operands)?;
 923                     }
 924
 925                     Array { .. } => {
 926                         let elem_size = match dest_ty.sty {
 927                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty, self.substs()) as u64,
 928                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 929                                         kind, dest_ty),
 930                         };
 931                         let offsets = (0..).map(|i| i * elem_size);
 932                         self.assign_fields(dest, offsets, operands)?;
 933                     }
 934
 935                     General { discr, ref variants, .. } => {
 936                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 937                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 938                             let discr_size = discr.size().bytes() as usize;
 939                             self.memory.write_uint(dest, discr_val, discr_size)?;
 940
 941                             let offsets = variants[variant].offset_after_field.iter()
 942                                 .map(|s| s.bytes());
 943                             self.assign_fields(dest, offsets, operands)?;
 944                         } else {
 945                             panic!("tried to assign {:?} to Layout::General", kind);
 946                         }
 947                     }
 948
 949                     RawNullablePointer { nndiscr, .. } => {
 950                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 951                             if nndiscr == variant as u64 {
 952                                 assert_eq!(operands.len(), 1);
 953                                 let operand = &operands[0];
 954                                 let src = self.eval_operand(operand)?;
 955                                 let src_ty = self.operand_ty(operand);
 956                                 self.move_(src, dest, src_ty)?;
 957                             } else {
 958                                 assert_eq!(operands.len(), 0);
 959                                 self.memory.write_isize(dest, 0)?;
 960                             }
 961                         } else {
 962                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 963                         }
 964                     }
 965
 966                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
 967                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 968                             if nndiscr == variant as u64 {
 969                                 let offsets = iter::once(0)
 970                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
 971                                 try!(self.assign_fields(dest, offsets, operands));
 972                             } else {
 973                                 assert_eq!(operands.len(), 0);
 974                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
 975                                 let dest = dest.offset(offset.bytes() as isize);
 976                                 try!(self.memory.write_isize(dest, 0));
 977                             }
 978                         } else {
 979                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 980                         }
 981                     }
 982
 983                     CEnum { discr, signed, .. } => {
 984                         assert_eq!(operands.len(), 0);
 985                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 986                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 987                             let size = discr.size().bytes() as usize;
 988
 989                             if signed {
 990                                 self.memory.write_int(dest, val as i64, size)?;
 991                             } else {
 992                                 self.memory.write_uint(dest, val, size)?;
 993                             }
 994                         } else {
 995                             panic!("tried to assign {:?} to Layout::CEnum", kind);
 996                         }
 997                     }
 998
 999                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
1000                 }
1001             }
1002
1003             Repeat(ref operand, _) => {
1004                 let (elem_size, length) = match dest_ty.sty {
1005                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty, self.substs()), n),
1006                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
1007                 };
1008
1009                 let src = self.eval_operand(operand)?;
1010                 for i in 0..length {
1011                     let elem_dest = dest.offset((i * elem_size) as isize);
1012                     self.memory.copy(src, elem_dest, elem_size)?;
1013                 }
1014             }
1015
1016             Len(ref lvalue) => {
1017                 let src = self.eval_lvalue(lvalue)?;
1018                 let ty = self.lvalue_ty(lvalue);
1019                 let len = match ty.sty {
1020                     ty::TyArray(_, n) => n as u64,
1021                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
1022                         n
1023                     } else {
1024                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
1025                     },
1026                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
1027                 };
1028                 self.memory.write_usize(dest, len)?;
1029             }
1030
1031             Ref(_, _, ref lvalue) => {
1032                 let lv = self.eval_lvalue(lvalue)?;
1033                 self.memory.write_ptr(dest, lv.ptr)?;
1034                 match lv.extra {
1035                     LvalueExtra::None => {},
1036                     LvalueExtra::Length(len) => {
1037                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
1038                         self.memory.write_usize(len_ptr, len)?;
1039                     }
1040                     LvalueExtra::DowncastVariant(..) =>
1041                         panic!("attempted to take a reference to an enum downcast lvalue"),
1042                 }
1043             }
1044
1045             Box(ty) => {
1046                 let size = self.type_size(ty, self.substs());
1047                 let ptr = self.memory.allocate(size);
1048                 self.memory.write_ptr(dest, ptr)?;
1049             }
1050
1051             Cast(kind, ref operand, dest_ty) => {
1052                 let src = self.eval_operand(operand)?;
1053                 let src_ty = self.operand_ty(operand);
1054
1055                 use rustc::mir::repr::CastKind::*;
1056                 match kind {
1057                     Unsize => {
1058                         self.move_(src, dest, src_ty)?;
1059                         let src_pointee_ty = pointee_type(src_ty).unwrap();
1060                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
1061
1062                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
1063                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
1064                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
1065                                 self.memory.write_usize(len_ptr, length as u64)?;
1066                             }
1067
1068                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1069                         }
1070                     }
1071
1072                     Misc => {
1073                         // FIXME(solson): Wrong for almost everything.
1074                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
1075                         self.memory.copy(src, dest, size)?;
1076                     }
1077
1078                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1079                 }
1080             }
1081
1082             Slice { .. } => unimplemented!(),
1083             InlineAsm { .. } => unimplemented!(),
1084         }
1085
1086         Ok(())
1087     }
1088
1089     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
1090         // Skip the constant 0 at the start meant for LLVM GEP.
1091         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
1092
1093         // Handle the field index for the outer non-null variant.
1094         let inner_ty = match ty.sty {
1095             ty::TyEnum(adt_def, substs) => {
1096                 let variant = &adt_def.variants[nndiscr as usize];
1097                 let index = path.next().unwrap();
1098                 let field = &variant.fields[index];
1099                 field.ty(self.tcx, substs)
1100             }
1101             _ => panic!(
1102                 "non-enum for StructWrappedNullablePointer: {}",
1103                 ty,
1104             ),
1105         };
1106
1107         self.field_path_offset(inner_ty, path)
1108     }
1109
1110     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
1111         let mut offset = Size::from_bytes(0);
1112
1113         // Skip the initial 0 intended for LLVM GEP.
1114         for field_index in path {
1115             let field_offset = self.get_field_offset(ty, field_index)?;
1116             ty = self.get_field_ty(ty, field_index)?;
1117             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
1118         }
1119
1120         Ok(offset)
1121     }
1122
1123     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
1124         match ty.sty {
1125             ty::TyStruct(adt_def, substs) => {
1126                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
1127             }
1128
1129             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1130             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1131             ty::TyBox(ty) => {
1132                 assert_eq!(field_index, 0);
1133                 Ok(ty)
1134             }
1135             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
1136         }
1137     }
1138
1139     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
1140         let layout = self.type_layout(ty, self.substs());
1141
1142         use rustc::ty::layout::Layout::*;
1143         match *layout {
1144             Univariant { .. } => {
1145                 assert_eq!(field_index, 0);
1146                 Ok(Size::from_bytes(0))
1147             }
1148             FatPointer { .. } => {
1149                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
1150                 Ok(Size::from_bytes(bytes as u64))
1151             }
1152             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
1153         }
1154     }
1155
1156     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
1157         use rustc::mir::repr::Operand::*;
1158         match *op {
1159             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
1160             Constant(mir::Constant { ref literal, ty, .. }) => {
1161                 use rustc::mir::repr::Literal::*;
1162                 match *literal {
1163                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1164                     Item { def_id, substs } => {
1165                         if let ty::TyFnDef(..) = ty.sty {
1166                             Err(EvalError::Unimplemented("unimplemented: mentions of function items".to_string()))
1167                         } else {
1168                             let cid = ConstantId {
1169                                 def_id: def_id,
1170                                 substs: substs,
1171                                 kind: ConstantKind::Global,
1172                             };
1173                             Ok(*self.statics.get(&cid).expect("static should have been cached (rvalue)"))
1174                         }
1175                     },
1176                     Promoted { index } => {
1177                         let cid = ConstantId {
1178                             def_id: self.frame().def_id,
1179                             substs: self.substs(),
1180                             kind: ConstantKind::Promoted(index),
1181                         };
1182                         Ok(*self.statics.get(&cid).expect("a promoted constant hasn't been precomputed"))
1183                     },
1184                 }
1185             }
1186         }
1187     }
1188
1189     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1190         use rustc::mir::repr::Lvalue::*;
1191         let ptr = match *lvalue {
1192             ReturnPointer => self.frame().return_ptr
1193                 .expect("ReturnPointer used in a function with no return value"),
1194             Arg(i) => self.frame().locals[i as usize],
1195             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1196             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1197
1198             Static(def_id) => {
1199                 let substs = self.tcx.mk_substs(subst::Substs::empty());
1200                 let cid = ConstantId {
1201                     def_id: def_id,
1202                     substs: substs,
1203                     kind: ConstantKind::Global,
1204                 };
1205                 *self.statics.get(&cid).expect("static should have been cached (lvalue)")
1206             },
1207
1208             Projection(ref proj) => {
1209                 let base = self.eval_lvalue(&proj.base)?;
1210                 let base_ty = self.lvalue_ty(&proj.base);
1211                 let base_layout = self.type_layout(base_ty, self.substs());
1212
1213                 use rustc::mir::repr::ProjectionElem::*;
1214                 match proj.elem {
1215                     Field(field, _) => {
1216                         use rustc::ty::layout::Layout::*;
1217                         let variant = match *base_layout {
1218                             Univariant { ref variant, .. } => variant,
1219                             General { ref variants, .. } => {
1220                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1221                                     &variants[variant_idx]
1222                                 } else {
1223                                     panic!("field access on enum had no variant index");
1224                                 }
1225                             }
1226                             RawNullablePointer { .. } => {
1227                                 assert_eq!(field.index(), 0);
1228                                 return Ok(base);
1229                             }
1230                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1231                             _ => panic!("field access on non-product type: {:?}", base_layout),
1232                         };
1233
1234                         let offset = variant.field_offset(field.index()).bytes();
1235                         base.ptr.offset(offset as isize)
1236                     },
1237
1238                     Downcast(_, variant) => {
1239                         use rustc::ty::layout::Layout::*;
1240                         match *base_layout {
1241                             General { discr, .. } => {
1242                                 return Ok(Lvalue {
1243                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1244                                     extra: LvalueExtra::DowncastVariant(variant),
1245                                 });
1246                             }
1247                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1248                                 return Ok(base);
1249                             }
1250                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1251                         }
1252                     },
1253
1254                     Deref => {
1255                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1256                         let ptr = self.memory.read_ptr(base.ptr)?;
1257                         let extra = match pointee_ty.sty {
1258                             ty::TySlice(_) | ty::TyStr => {
1259                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1260                                 let len = self.memory.read_usize(len_ptr)?;
1261                                 LvalueExtra::Length(len)
1262                             }
1263                             ty::TyTrait(_) => unimplemented!(),
1264                             _ => LvalueExtra::None,
1265                         };
1266                         return Ok(Lvalue { ptr: ptr, extra: extra });
1267                     }
1268
1269                     Index(ref operand) => {
1270                         let elem_size = match base_ty.sty {
1271                             ty::TyArray(elem_ty, _) |
1272                             ty::TySlice(elem_ty) => self.type_size(elem_ty, self.substs()),
1273                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1274                         };
1275                         let n_ptr = self.eval_operand(operand)?;
1276                         let n = self.memory.read_usize(n_ptr)?;
1277                         base.ptr.offset(n as isize * elem_size as isize)
1278                     }
1279
1280                     ConstantIndex { .. } => unimplemented!(),
1281                 }
1282             }
1283         };
1284
1285         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1286     }
1287
1288     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1289         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx), self.substs())
1290     }
1291
1292     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1293         self.monomorphize(self.mir().operand_ty(self.tcx, operand), self.substs())
1294     }
1295
1296     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1297         let size = self.type_size(ty, self.substs());
1298         self.memory.copy(src, dest, size)?;
1299         if self.type_needs_drop(ty) {
1300             self.memory.drop_fill(src, size)?;
1301         }
1302         Ok(())
1303     }
1304
1305     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1306         use syntax::ast::{IntTy, UintTy};
1307         let val = match (self.memory.pointer_size, &ty.sty) {
1308             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1309             (_, &ty::TyInt(IntTy::I8))    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1310             (2, &ty::TyInt(IntTy::Is)) |
1311             (_, &ty::TyInt(IntTy::I16))   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1312             (4, &ty::TyInt(IntTy::Is)) |
1313             (_, &ty::TyInt(IntTy::I32))   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1314             (8, &ty::TyInt(IntTy::Is)) |
1315             (_, &ty::TyInt(IntTy::I64))   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1316             (_, &ty::TyUint(UintTy::U8))  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1317             (2, &ty::TyUint(UintTy::Us)) |
1318             (_, &ty::TyUint(UintTy::U16)) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1319             (4, &ty::TyUint(UintTy::Us)) |
1320             (_, &ty::TyUint(UintTy::U32)) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1321             (8, &ty::TyUint(UintTy::Us)) |
1322             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1323
1324             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
1325             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
1326                 if self.type_is_sized(ty) {
1327                     match self.memory.read_ptr(ptr) {
1328                         Ok(p) => PrimVal::AbstractPtr(p),
1329                         Err(EvalError::ReadBytesAsPointer) => {
1330                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1331                         }
1332                         Err(e) => return Err(e),
1333                     }
1334                 } else {
1335                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1336                 }
1337             }
1338
1339             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1340         };
1341         Ok(val)
1342     }
1343
1344     fn frame(&self) -> &Frame<'a, 'tcx> {
1345         self.stack.last().expect("no call frames exist")
1346     }
1347
1348     fn basic_block(&self) -> &mir::BasicBlockData<'tcx> {
1349         let frame = self.frame();
1350         frame.mir.basic_block_data(frame.next_block)
1351     }
1352
1353     fn frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
1354         self.stack.last_mut().expect("no call frames exist")
1355     }
1356
1357     fn mir(&self) -> CachedMir<'a, 'tcx> {
1358         self.frame().mir.clone()
1359     }
1360
1361     fn substs(&self) -> &'tcx Substs<'tcx> {
1362         self.frame().substs
1363     }
1364 }
1365
1366 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1367     match ptr_ty.sty {
1368         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1369         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1370         ty::TyBox(ty) => {
1371             Some(ty)
1372         }
1373         _ => None,
1374     }
1375 }
1376
1377 impl Lvalue {
1378     fn to_ptr(self) -> Pointer {
1379         assert_eq!(self.extra, LvalueExtra::None);
1380         self.ptr
1381     }
1382 }
1383
1384 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1385     type Target = mir::Mir<'tcx>;
1386     fn deref(&self) -> &mir::Mir<'tcx> {
1387         match *self {
1388             CachedMir::Ref(r) => r,
1389             CachedMir::Owned(ref rc) => rc,
1390         }
1391     }
1392 }
1393
1394 #[derive(Debug)]
1395 pub struct ImplMethod<'tcx> {
1396     pub method: Rc<ty::Method<'tcx>>,
1397     pub substs: &'tcx Substs<'tcx>,
1398     pub is_provided: bool,
1399 }
1400
1401 /// Locates the applicable definition of a method, given its name.
1402 pub fn get_impl_method<'a, 'tcx>(
1403     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1404     impl_def_id: DefId,
1405     substs: &'tcx Substs<'tcx>,
1406     name: ast::Name,
1407 ) -> ImplMethod<'tcx> {
1408     assert!(!substs.types.needs_infer());
1409
1410     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1411     let trait_def = tcx.lookup_trait_def(trait_def_id);
1412
1413     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1414         Some(node_item) => {
1415             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1416                 let substs = traits::translate_substs(&infcx, impl_def_id,
1417                                                       substs, node_item.node);
1418                 tcx.lift(&substs).unwrap_or_else(|| {
1419                     bug!("trans::meth::get_impl_method: translate_substs \
1420                           returned {:?} which contains inference types/regions",
1421                          substs);
1422                 })
1423             });
1424             ImplMethod {
1425                 method: node_item.item,
1426                 substs: substs,
1427                 is_provided: node_item.node.is_from_trait(),
1428             }
1429         }
1430         None => {
1431             bug!("method {:?} not found in {:?}", name, impl_def_id)
1432         }
1433     }
1434 }
1435
1436 pub fn interpret_start_points<'a, 'tcx>(
1437     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1438     mir_map: &MirMap<'tcx>,
1439 ) {
1440     let initial_indentation = ::log_settings::settings().indentation;
1441     for (&id, mir) in &mir_map.map {
1442         for attr in tcx.map.attrs(id) {
1443             use syntax::attr::AttrMetaMethods;
1444             if attr.check_name("miri_run") {
1445                 let item = tcx.map.expect_item(id);
1446
1447                 ::log_settings::settings().indentation = initial_indentation;
1448
1449                 debug!("Interpreting: {}", item.name);
1450
1451                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1452                 match gecx.call(mir, tcx.map.local_def_id(id)) {
1453                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
1454                         gecx.memory.dump(return_ptr.alloc_id);
1455                     },
1456                     Ok(None) => warn!("diverging function returned"),
1457                     Err(_e) => {
1458                         // TODO(solson): Detect whether the error was already reported or not.
1459                         // tcx.sess.err(&e.to_string());
1460                     }
1461                 }
1462             }
1463         }
1464     }
1465 }
1466
1467 // TODO(solson): Upstream these methods into rustc::ty::layout.
1468
1469 trait IntegerExt {
1470     fn size(self) -> Size;
1471 }
1472
1473 impl IntegerExt for layout::Integer {
1474     fn size(self) -> Size {
1475         use rustc::ty::layout::Integer::*;
1476         match self {
1477             I1 | I8 => Size::from_bits(8),
1478             I16 => Size::from_bits(16),
1479             I32 => Size::from_bits(32),
1480             I64 => Size::from_bits(64),
1481         }
1482     }
1483 }
1484
1485 trait StructExt {
1486     fn field_offset(&self, index: usize) -> Size;
1487 }
1488
1489 impl StructExt for layout::Struct {
1490     fn field_offset(&self, index: usize) -> Size {
1491         if index == 0 {
1492             Size::from_bytes(0)
1493         } else {
1494             self.offset_after_field[index - 1]
1495         }
1496     }
1497 }